Belted suction box arrangement



March 20, 1962 E. D. BEACHLER ETAL BELTED SUCTION BOX ARRANGEMENT Filed Nov. 19, 1958 3 Sheets$heet 1 fn e'nfurz EDWAPD 0. 9540410512 500%? v JUSfZ/S March 20, 1962 E, D BEACHLER ET'AL 3,025,910

' BELTED SUCTION BOX ARRANGEMENT Filed NOV. 19, 1958 m 3 Sheets-Sheet 2 ZUVEZZ/UPE EDS/4Q J. JUSTUS @WM H17 5.

50mm 0 2540mm March 20, 1962 E. D. BEACHLER ETAL 3,025,910

BELTED SUCTION BOX ARRANGEMENT Filed Nov. 19, 1958 3 Sheets$heet 5 EDWAQD 0 BEAU/LEE 06 442 d. JUSTZ/S atet The present invention relates to a water removal device for a paper machine, and more particularly to an improved belt construction and support therefor for dewatering a suspension of paper stock flowing on the surface of a Fourdrinier type wire overlying the belt.

In a conventional Fourdrinier type of paper-making machine, a dilute suspension of paper stock is caused to flow onto a forming wire, and excess water is drained through the wire to deposit the layer of stock fibers on the wire surface. The wire is conventionally supported by a suction box and spaced table rolls or the like and water drainage occurs through the wire to subatmo-sphere pressures in the suction box. The friction between the wire and the box as the wire is drawn over the open top of the box is substantial, and is increased by the suction Within the box. The conventional suction flat box applies intermittent forces to the stock on the wire as the wire travels over the hole areas and land areas which are provided by the support for the wire at the top of the suction box. The fiat, or suction boxes of the conventional Fourdrinier wear rapidly from frictional contact with the wire, necessitating frequent regrinding or planing of their surfaces. For removal, for fastening, and for such machining, such flat box surfaces are limited in width (along the machine direction) and are spaced apart.

A feature of the invention is the provision of a belted support structure for carrying the wire which greatly reduces friction forces and which has the ability to more effectively dewater paper webs on the wire. The structure makes possible reduction in length of the required suction area and reduces the friction effect of the Fourdrinier wire as it travels over the suction box. The arrangement also contemplates effectively dewatering heavier multiple webs on the wire within relatively short lengths of wire travel.

An object of the invention is to provide an improved Fourdrinier wire supporting belt and suction box structure capable of applying a continuous suction to dewater a web of paper deposited on the surface of the wire, and to apply a uniform suction over the width.

A further object of the invention is to provide an improved and more effective dewatering mechanism for forming a paper web employing a Fourdrinier wire supported by a suction belt in the form of a looped belt of rubber or like material, which requires a shorter length of dewatering area and which has reduced friction drag between the belt and a supporting suction box.

Another object of the invention is to provide an improved wire supporting belt and suction box structure for dewatering paper web with a variable deckle having improved features for adjustment of the deckle, and for forming a uniform web to the adjustable deckle edge.

A still further object of the invention is to provide a dewatering mechanism for forming a paper web from a suspension of paper stock by depositing the stock on a traveling wire but eliminating the usual friction of the wire on a supporting suction box providing a unitary suction box and eliminating the necessity for intermediate table rolls or spaces.

A further object of the invention is to, provide an improved dewatering belt for supporting a wire for dewatering a paper web having a construction for more effective dewatering and which may be formed of a molded rubber or like material.

Other objects and advantages will become more apparent with the teachings of the principles of the invention in connection with the disclosure of the preferred embodiments thereof, in the specification, claims and drawings, in which:

FIGURE 1 is a side elevational view shown partially in diagrammatic form, of a paper web dewatering mechanism adapted for use with a Fourdrinier type of papermaking machine embodying the principles of the present invention;

FIGURE 2 is an enlarged, detailed, top plan view showing the arrangement of the top of a suction box for the dewatering mechanism;

FIGURE 3 is an enlarged, detailed, vertical sectional View taken along line III-III of FIGURE 5 of the drawrugs;

FIGURE 4 is a vertical sectional view taken substantially along line IV-IV of FIGURE 2, and including a suction belt embodying the principles of the present invention;

FIGURE 5 is a top plan view of a portion of the suction belt showing the arrangement of the top surface; and,

FIGURES 6, 7 and 8 are vertical sectional views similar to FIGURE 4, and illustrating different positions of adjustment for changing the deckle edge of the paper web.

As shown on the drawings:

As illustrated in FIGURE 1, the mechanism in general for dewatering a paper web on a traveling forming wire W, which in the present preferred embodiment, is supported by a looped belt 11. having molded grooves or channels in the upper surface with ports opening to the lower surface, as will be explained in detail in connection with FIGURES 3, 4 and 5.

The looped belt 11 travels over a suction box 12 and is supported on the top 13 thereof for the run 11a, during which time the dewatering occurs. A salient feature of the present invention is the improved dewatering effect.

which can be achieved in the improved construction of the belt and suction box which makes it possible to provide a unitary suction box. This greatly reduces the space required for the dewatering phase of operations in the entire paper-making process, and obviates the necessity of providing separate suction boxes with supporting table rolls and/or spaces therebetween.

The looped suction belt 11 is carried on conventional rolls 14 and 16, respectively, and guide rolls 17 and. 1.8 are positioned to support the lower run 11b of the belt. The guide roll 18 may be supported and operated so as to be pivotal about one end, with the other end moving in the directions indicated by the arrows 19 and 21. With this operation of the guide roll 18, the lateral position of the belt 11 can be accurately controlled and guided so as to maintain the belt in a positive lateral, position with respect to the suction box 12'. This is important in insuring that the belt 11 will have a fixed lateral position for purposes of alignment of drain passageways, as will later become more apparent.

A suspension of paper stock is let onto the traveling wire W from a headbox (not shown) in the usual manner. rSuitable connections, not shown, are provided for the drainage of water from the suction box 12, and for applying a vacuum thereto.

The belt, as particularly shown in FIGURES 3, 4 and 5, is formed of a molded material, such as rubber, which is well adapted for forming the improved top surface conformation for dewatering and drainage, as will be described, and which has reduced friction between its lower surface 24 and the top 13 of the suction box when wetted with the Water being drawn from the paper web, which lies on the upper surface 23 of the belt.

Formed in the upper surface 23 is a plurality of grooves or channels, as illustrated at 24, 26, 27, 28, 29, 31, 32 and 33, FIGURE 5. These channels are elongated with straight sides and extend laterally across the belt 11. The channels are arranged in straight rows extending laterally across the belt 11, and as illustrated in FIGURE 5, channels 26 and 33 illustrate the end of one lateral row, channels 27 and 31 illustrate the end of another row, and channels 28 and 32 illustrate the end of still another row.

The channels may also be regarded as being arranged in longitudinal rows. The channels of each longitudinal row, however, are staggered so as to extend halfway into the adjacent row. For example, channels 33, 31 and 32 lie in one longitudinal row (the longitudinal row extending in the direction of belt travel, as indicated by the arrow 34). The channels 26, 27 and 28 may be regarded as forming another longitudinal row. It will thus be noted that the channel 31 extends laterally beyond its row into the other row, and that the channels 26 and 28 extend laterally into the row adjacent to their row. It will be understood that channels 26 and 28, as well as channels 33, 31 and 32, represent channels of full length. The channel 27 is only one-half length in order to form 'an even edge of the channel area, with the edge of the main channel area being defined by the ends 26a, 27a and 28a.

The channels are thus arranged so that they alternately overlap. In other words, in a longitudinal direction, each channel is offset from its adjacent channel to overlap onehalf of the adjacent channel. This will cause drainage of an area in both lateral directions, since the drainage ports for each channel are located at the centers of the channels. The drainage port for the channel 26 is shown at 36, the drainage port for the channel 28 is shown at 38, and the drainage port for the channel 31 is shown at 39. The drainage port for the channel 27 is shown at 37.

Each drainage port extends downwardly from the base of the channel and opens through the lower surface 29 of the belt to communicate with the suction box for the drainage of water. As illustrated by the port 38, a lower oblong straight walled portion 38a opens through the lower surface 20 of the belt, and the port is provided with an upper outwardly flaring tapered portion 38b which is wider than the channel 28 which it drains. Likewise, the port 36 is provided with a straight walled lower portion 36a which opens into the suction box from the lower surface 20 of the belt, and an outwardly flaring tapered upper portion 36b which is wider than the channel 26 which it drains. The drainage ports are so located as to be opposite the ends of the channels in an adjacent lateral row. Thus, the ports 36 and 38 are opposite the ends 2711 and 31a of the channels 27 and 31 of the lateral row intermediate the rows of channels 26 and 28. This arrangement of the ports improves drainage from each of the channels and assures uniform and improved suction on the web for improved and uniform dewatering. Thus, the port 39 for the channel 31 is at the midpoint of the channel 31, and located opposite the ends of the channels of the adjacent lateral rows, that is, the ends of channels 26 and 33, and the ends of channels 28 and 32.

This configuration furthermore provides a contact surface for the supported Fourdrinier wire, having minimum area, so as to offer minimal resistance to the removal of water from the web being formed.

Each of the channels has an improved shape for improved suction and drainage. As illustrated in FIGURE 3, the channel 26 has a base planar portion 2611. Rising upwardly and diverging outwardly from the planar base are inclined side walls 260 and 26d. Rising upwardly from the upper edges of the side walls 260 and 26d are vertical side walls 26e and 26 which extend to the top surface 23 of the belt. Inasmuch as each of the channels 4 is of similar construction, only one need be described in detail, with each having an identical cross-sectional shape.

Outwardly of the aforedescribed channels aresecond shorter channels or deckle channels, as illustrated at 41, 42, 43 and 44 in FIGURE 5. The deckle channels are shorter and are of substantially the same cross-sectional configuration with a planar base 41a and outwardly diverging side walls 41b and 410 and straight vertical side walls 41:: and 41] adjacent the top surface of the belt. Since the deckle channels are shorter and taper to a point at their ends, they have a generally oblong shape, as contrasted with the longer channels which have straight sides. The deckle channels are arranged so that they extend in longitudinal rows with channels 41 and 43 being located in the outer row and channels 42 and 44 located in the inner longitudinal row. The deckle channels are also arranged so that the channels of the outer row are aligned laterally with the lateral rows of the longer channels, and the deckle channels of the inner rows are between the rows of the longer channels. Thus, deckle channel 41 is aligned with the row of the longer channel 26, and deckle channel 43 is aligned with the row of the longerchannel 27. Deckle channels 42 and 44 extend between the rows. Their inner ends 42a and 44a project into the longitudinal rows of the longer channels, or in other words, project beyond the ends 26a, 27a and 28a which define the edge of the area of the longer channels.

Each of the deckle channels is provided with a port opening from the base through the lower surface of the belt. Thus, channels 41, 42, 43 and 44 have drainage ports 48, 49, 51 and 52 opening from the bottom thereof.

In determining the width of the paper web formed on the upper surface of the belt, vacuum is selectively applied to the inner row of deckle channels and the outer row of deckle channels. For a paper web of narrow width, the vacuum from the suction box is cut off to the ports 49 and 52, and the rest of the row of inner deckle channels, and also from the outer row of deckle channels.

- For an intermediate width of paper web, vacuum is applied to the inner row of deckle channels. For a full wide width of paper web, vacuum is applied to both rows of deckle channels.

The top 13 of the suction box 12 which functions to support the traveling belt 11 and apply suction to the channels in the surface, is illustrated in detail in FIG- URES 2 and 4. At the end of the suction box top is shown a plate 53, being attached to the suction box by screws 54 and 56. Extending longitudinally along the top of the suction box and attached to form a sliding support surface for the belt 11, are bearing strips, as illustrated at 57, 58 and 59. The bearing strips are spaced apart and extend parallel to each other. Running longitudinally along the top of each bearing strip are grooves, as illustrated at 576.! and 57b for the bearing strip 57, and

58a and 58b for the bearing strip 58. These grooves reduce the area subjected to friction and admit water (or the like) for lubrication of the belt sliding over the bearing strips.

The grooves 57a, 57b, 58a and 58b provide channels through which water (or the like) may be introduced under pressure sufiicient to counter the effect of the atmospheric pressure acting on the wire and the belt. By supplying a slight excess of pressure, a film of water flows from the grooves into the drainage holes 570 and 580, lubricating the passage of the belt 11 over the surface of the suction box structure 12. Furthermore, such water film effectively seals against the ingress of atmospheric air.

Preferably these grooves are sized to occupy approximately fifty percent of the land area remaining around the suction holes.

Each bearing strip has a series of drainage openings, such as illustrated at 57c and 580 for the bearing strips 57 and 58. These openings are in lateral alignment with the drainage ports in the belt, and as illustrated in FIG- URE 4, the ports 37 and 38 in the belt draining through the rows of ports 57c and 58c. The bearing strips may be formed of various materials, and, by way of example, may be formed of metal or of a hard wood, such as maple, or other material which has good Wearing and friction characteristics for the purposes desired.

The bearing strips are supported by underlying support strips such as illustrated at 6'1 and 62. The support strips extend in spaced parallel relationship longitudinally along the top of the suction box, and form slots such as illustrated at 63 and 64, therebetween, which are in communication with the rows of holes through the bearing strips. The support strips are tied to each other by lugs with strips 61 and 62 tied by lug 68. The support strip 61 is tied to a side support plate 71 by lug 69. Screws such as 72, 73, 74 and 76 extend down through holes in the bearing strips and support strips to draw the lugs, support strips and bearing strips together.

On top of the support plate 71is a deckle plate or strip 79 which is mounted so as to slide laterally to a first, second or a third position. Lateral movement of the deckle strip 79 determines the width of the paper web being formed. The positions are illustrated in FIGURES 6, 7 and 8. In the first position, as illustrated in FIG- URE 6, the Widest web is formed. In the second position, as illustrated in FIGURE 7, the narrowest web is formed. In the intermediate position, as illustrated in FIGURE 8, a web of an intermediate width is formed.

As illustrated in FIGURE 4, the deckle strip 79 has a laterally extending slot 79a through which extends a guide bolt 80 threaded into the support plate 71. An upstanding lug 79b is positioned at the outer edge of the deckle strip 79, and is threaded to receive a rotational adjustment bolt 81. The bolt is rotatable in a support lug 82 which is secured to the support plate 71, and rotation of the bolt will permit adjustment of the deckle strip 79. A lock nut 83 threads against the lug 79 to lock the position of the deckle strip. It will be understood that a plurality of adjustment bolts 81 may be provided along the deckle strip for uniform adjustment of the deckle strip.

The deckle strip is provided with three rows of holes, with an inner row illustrated at 84, an intermediate row at 86, and an outer row at 87, as illustrated particularly in FIGURES 2 and 4. These rows of deckle holes have blocking areas therebetween with a blocking area 88 between the holes 84 and 86 and a blocking area 89 between the rows of holes 86 and 87. The holes and blocking areas therebetween either make communication or block communication between the slots 77 and 78 in the support plate and the inner and outer rows of deckle channels in the belt.

As illustrated in FIGURE 6, the deckle plate 79 is positioned in its innermost position so that the rows 86 and 87 of deckle holes provide communication between the slot 77 and the port 52, leading to the channel 44 which is in the inner row of deckle channels. The deckle holes 87 provide communication between the slot 78 and the plate 71 and the port 51 leading to the deckle channel 43, which is in the outer row of deckle channels.

FIGURE 7 illustrates the deckle strip 79 moved outwardly to the next adjusted position. In this position,

which forms the narrowest web of paper, the slots 77 in the support plate 71 are blocked by the area 89 and the inner row of deckle ports in the belt is blocked by the area 88.

As illustrated in FIGURE 8, in the outermost position of the deckle plate 79, the blocking area 89 still blocks the outer slot 7 8 in the support plate, but the inner slot 77 communicates through the inner row of deckle holes with the port 52 leading to the channel 44 which is in the inner row of deckle channels. In either position of the deckle plate 79, a uniform web of paper is formed to the deckle edge because of the improved and more uniform drainage path for the water being drawn from the web.

In operation, the looped suction belt 11 is driven over the top 13 of the suction box 12, and water is drained from a web formed by a deposit of paper solution on the top surface of the wire W. The web is dewatered and compacted by water draining from the overlying Wire into the main channels which are formed in the top surface of the belt 11, and which are arranged in lateral rows, as illustrated by the channels 26 and 33, and are arranged in longitudinal rows, as illustrated by the channels 33 and 31, with alternate channels such as 31 offset one-half length to extend into the adjacent row. Each channel is provided with a centrally located drainage port, as indicated by the port 39 for the channel 31. The edge of the web is formed by the deckle channels which are arranged in an inner row, as illustrated by the channel 44, and an outer row, as illustrated by the channel 43. Variation of the deckle edge is obtained by positioning the deckle strip 79 in one of the positions of FIGURES 6, 7 and 8, to provide communication between the inner and/or outer rows of channels in the belt, and the slots 77 and 78 in the support plate 71.

Thus it will be seen that we have provided a dewatering mechanism providing for improved more uniform and more rapid drainage which achieves the attendant advantages hereinabove set forth. The apparatus makes possible the provision of a belt and suction box arrangement in a paper forming machine which has reduced friction between the belt and suction box and which permits a more compact structure for the machine in providing a much shorter length of travel for the dewatering operation. The provision of a unitary suction box without intermediate supporting table rolls or spaces achieves other attendant advantages in more compact equipment, and enables the provision of a simplified machine in which the belt may be more easily changed.

We have, in the drawings and specification, presented a detailed disclosure of the preferred embodiments of our invention, and it is to be understood that we do not intend to limit the invention to the specific form disclosed, but intend to cover all modifications, changes and alternative constructions and methods falling within the scope of the principles taught by our invention.

We claim as our invention:

1. An apparatus for extracting water from a suspension of paper stock in a paper machine comprising a suction box having a top supporting surface with openings for draining water, rolls positioned to support a belt traveling over the box, an endiess belt loop trained over said rolls with a run supported by the suction box top to travel over the box and to support a Fourdrinier wire on the upper surface of the belt, said belt characterized by having a substantially planar upper surface extending to outer side edges and having a plurality of elongated first channels in the surface extending transversely of the belt with a drainage port opening through the belt to the lower surface thereof from the base of each of said channels communicating with said suction box openings, said channels arranged in longitudinal rows, said channels of adjacent rows being transversely staggered and extending into adjoining rows to overlap the rows, and further characterized by a plurality of elongated second channels in the upper belt surface shorter than said first channels and also extending transversely of the belt and arranged in longitudinal rows with a port opening downwardly through the lower surface of the belt from each of said second channels, said second channels being located outside of said first channels with respect to the outer edge of the belt, said second channels being transversely staggered with respect to said channels and adjoining rows with the ends extending into adjoining rows so as to overlap said first channels and said second channels in the rows adjoining each other being staggered so that the rows overlap to form an even dewatering between said first and second channels, and means for applying a suction to the ports at the underside of the belt leading to said 7 second channels of a selective number of rows outwardly of said first channels leaving the remainder of the second channels Without suction to define a deckle edge.

2. An apparatus for extracting water from a suspension of paper stock in a paper machine comprising a suction box having a top supporting surface with openings for draining water, rolls positioned to support a belt trav cling over the box, and an endless rubber belt loop strung over said rolls and supported on said suction box top for carrying a wire for supporting a paper web, said belt characterized by being provided with a plurality of short molded channels in the upper surface extending transversely of the direction of travel of the belt, said channels arranged in longitudinal rows with the ends of the channels in each row projecting a substantial distance into the adjacent row so that the water will be extracted into both rows in the area of overlap, and ports provided in the base of each of the channels opening through the lower surface of the belt to drain the channels;

3. In a dewatering mechanism for forming a paper Web from a paper stock by depositing the stock on a non zontal perforate traveling wire passing over a suction box, an improved endless rubber belt for supporting the wire on the upper surface having a plurality of elongated channels in the upper surface extending parallel to each other transversely of the direction of belt movement, the channels characterized by having the ends tapering inwardly, a flat horizontal planar surface of a width less than the channel located in the bottom thereof, side walls rising from said planar surface tapering outwardly and upwardly to the full width of the channel, vertical side walls extending vertically upwardly from said tapered side walls to the top surface of the belt, and ports opening through the lower surface of the belt from the base of the channels for drainage ofthe channels.

4. In a dewateririg mechanism for forming a paper web from a paper stock by depositing the stock on a horizontal traveling Four'drinier wire passing over a suction box, an improved endless rubber belt forsupporting the wire on the upper surface having a plurality of elongated chanriels in the upper surface extending parallel to each other transversely of the direction of belt movement, the channels being arranged in longitudinal rows, the channels characterized by having straight sides each parallel to the sides of an adjoining channel in the same row and having tapered ends, alternate channels of each row being transversely staggered to project into an adjacent row with first and third rows separated by a second row and channels of said first and third rows extending sufiiciently into the second row so that the ends of channels of said first and third rows are adjoining, ports opening through the bottom of the belt from each of the channels, said ports of said second row located intermediate the ends of the channel drained by it and located at the location Where the ends of the channels of the first and third rows are positioned for improved dewatering.

5. In a dewatering mechanism for forming a paper web from a paper stock by depositing the stock on a horizontal perforate traveling Fourdrinier wire passing over a suction box, an improved endless rubber belt for supporting the Wire on an upper surface having a plurality of elongated channels in the upper surface extending parallel to each other transversely of the longitudinal direction of belt movement, a plurality of said channels being of substantially equal length extending transversely across the belt in aligned rows, said channels being transversely staggered in position with the channels ahead and behind each channel in the longitudinal direction of belt movement shifted to transversely overlap one-half the channel length and with the ends of the channels located substantially midway between the channels longitudinally ahead and behind in the direction of belt travel, and a drainage port for each channel opening from the bottom surface of the belt and located at the midpoint of the channel and provided with an enlarged upper end extending beyond the sides of the channel at the location Where the ends of the channels longitudinally ahead and behind the ported channel are located.

6. A mechanism for forming a paper web by dewatering paper stock on a traveling Fourdrinier wire which comprises a suction box, rolls positioned to support a belt traveling over the box, an endless looped belt for supporting a wire and having perforations extending therethrough with deckle perforations at the edges and being trained over said rolls to travel over the box, said deckle preforations in the belt arranged in rows along the belt edge extending in the direction of belt travel, a support plate at the top of the box having openings spaced apart to coincide with the spacing of the rows of deckle perforations, and a deckle strip means between said support plate and said belt with openings therein spaced for selectively communicating additional outwardly successive roWs of deckle perforations with said support plate openings with change in adjustment of the position of said deckle strip means.

7. A mechanism for forming a paper web by dewatering paper stock deposited on a traveling Fourdrinier wire which comprises a suction box, breast and couch rolls positioned to support a belt traveling over the box, an endless looped belt for supporting a wire and having dewatering perforations extending therethrough with inner and outer rows of deckle perforations extending along a side edge, a support plate positioned beneath the outer edge of the belt and having inner and outer openings spaced laterally to coincide with said rows of belt perforations and communicating with the interior of the box, a deckle plate positioned between the belt and the support plate and slidingly supported on the support plate and having first, second and third openings arranged successively outwardly for providing communication between said deckle perforations and said perforations in the support plate, and means for moving said deckle plate outwardly to a first, second or third position; said openings in the deckle plate positioned to align said second and third openings with said inner and with said outer openings in said support plate respectively and with said inner and with said outer deckle perforations respectively to form a wide web in said first position; to align the blocking areas between said first and second openings and between said second and third openings in said deckle plate with said inner and outer openings in said support plate respectively and with said inner and outer deckle perforations respectively in said second position to form a narrow Web; and to align said first opening in said deckle plate with said inner deckle perforation and with said inner opening in said support plate, and the space between said second and third openings in the deckle plate with said outer deckle perforation and with said outer openings in said deckle plate in said third position for forming a web of intermediate width.

8. In a dewatering mechanism for forming a paper web from a paper stock by depositing the stock on a Fourdrinier wire carried on a horizontal perforate traveling belt passing over a suction box, an improved endless rubber belt having a plurality of elongated channels in the upper surface extending parallel to each other transversely of the direction of belt movement, a plurality of said channels being of substantially equal length extending across the belt in aligned rows, said channels being staggered in position with the channels ahead and behind each channel in the longitudinal direction of belt move ment shifted to transversely overlap one-half the chan nel length and with the ends of the channels located sub stantially midway between the channels longitudinally ahead and behind, a drainage port for each channel opening from the bottom surface of the belt and located at the midpoint of the channel and provided with an enlarged upper end extending beyond the sides of the channel at the location where the ends of the channels longitudinally ahead and behind the ported channels are located, a plurality of separate support strips extending longitudinally and positioned at spaced intervals across the top of the box and defining suction slots therebetween, and hearing plates positioned over said suction slots and supporting said belt in sliding movement thereover, said plates having openings disposed therealong communicating with said slots and with said perforations for the drainage of water from a web on the wire carried on the belt.

References Cited in the file of this patent UNITED STATES PATENTS McGrath June 14, Clark Apr. 11, Evans June 24, Staudenmaier Apr. 8, 

